When KVM injects an exception into a guest, it generates the CPSR value from scratch, configuring CPSR.{M,A,I,T,E}, and setting all other bits to zero.
This isn't correct, as the architecture specifies that some CPSR bits are (conditionally) cleared or set upon an exception, and others are unchanged from the original context.
This patch adds logic to match the architectural behaviour. To make this simple to follow/audit/extend, documentation references are provided, and bits are configured in order of their layout in SPSR_EL2. This layout can be seen in the diagram on ARM DDI 0487E.a page C5-426.
Signed-off-by: Mark Rutland mark.rutland@arm.com Cc: Alexandru Elisei alexandru.elisei@arm.com Cc: Drew Jones drjones@redhat.com Cc: James Morse james.morse@arm.com Cc: Julien Thierry julien.thierry.kdev@gmail.com Cc: Marc Zyngier maz@kernel.org Cc: Peter Maydell peter.maydell@linaro.org Cc: Suzuki K Poulose suzuki.poulose@arm.com Cc: Will Deacon will@kernel.org Cc: stable@vger.kernel.org --- arch/arm/include/asm/kvm_emulate.h | 12 ++++ arch/arm64/include/asm/ptrace.h | 1 + virt/kvm/arm/aarch32.c | 110 +++++++++++++++++++++++++++++++++---- 3 files changed, 113 insertions(+), 10 deletions(-)
diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h index 40002416efec..dee2567661ed 100644 --- a/arch/arm/include/asm/kvm_emulate.h +++ b/arch/arm/include/asm/kvm_emulate.h @@ -14,13 +14,25 @@ #include <asm/cputype.h>
/* arm64 compatibility macros */ +#define PSR_AA32_MODE_FIQ FIQ_MODE +#define PSR_AA32_MODE_SVC SVC_MODE #define PSR_AA32_MODE_ABT ABT_MODE #define PSR_AA32_MODE_UND UND_MODE #define PSR_AA32_T_BIT PSR_T_BIT +#define PSR_AA32_F_BIT PSR_F_BIT #define PSR_AA32_I_BIT PSR_I_BIT #define PSR_AA32_A_BIT PSR_A_BIT #define PSR_AA32_E_BIT PSR_E_BIT #define PSR_AA32_IT_MASK PSR_IT_MASK +#define PSR_AA32_GE_MASK 0x000f0000 +#define PSR_AA32_PAN_BIT 0x00400000 +#define PSR_AA32_SSBS_BIT 0x00800000 +#define PSR_AA32_DIT_BIT 0x01000000 +#define PSR_AA32_Q_BIT PSR_Q_BIT +#define PSR_AA32_V_BIT PSR_V_BIT +#define PSR_AA32_C_BIT PSR_C_BIT +#define PSR_AA32_Z_BIT PSR_Z_BIT +#define PSR_AA32_N_BIT PSR_N_BIT
unsigned long *vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num);
diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index fbebb411ae20..bf57308fcd63 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -62,6 +62,7 @@ #define PSR_AA32_I_BIT 0x00000080 #define PSR_AA32_A_BIT 0x00000100 #define PSR_AA32_E_BIT 0x00000200 +#define PSR_AA32_PAN_BIT 0x00400000 #define PSR_AA32_SSBS_BIT 0x00800000 #define PSR_AA32_DIT_BIT 0x01000000 #define PSR_AA32_Q_BIT 0x08000000 diff --git a/virt/kvm/arm/aarch32.c b/virt/kvm/arm/aarch32.c index c4c57ba99e90..17bcde5c2451 100644 --- a/virt/kvm/arm/aarch32.c +++ b/virt/kvm/arm/aarch32.c @@ -10,6 +10,7 @@ * Author: Christoffer Dall c.dall@virtualopensystems.com */
+#include <linux/bits.h> #include <linux/kvm_host.h> #include <asm/kvm_emulate.h> #include <asm/kvm_hyp.h> @@ -28,22 +29,111 @@ static const u8 return_offsets[8][2] = { [7] = { 4, 4 }, /* FIQ, unused */ };
+/* + * When an exception is taken, most CPSR fields are left unchanged in the + * handler. However, some are explicitly overridden (e.g. M[4:0]). + * + * The SPSR/SPSR_ELx layouts differ, and the below is intended to work with + * either format. Note: SPSR.J bit doesn't exist in SPSR_ELx, but this bit was + * obsoleted by the ARMv7 virtualization extensions and is RES0. + * + * For the SPSR layout seen from AArch32, see: + * - ARM DDI 0406C.d, page B1-1148 + * - ARM DDI 0487E.a, page G8-6264 + * + * For the SPSR_ELx layout for AArch32 seen from AArch64, see: + * - ARM DDI 0487E.a, page C5-426 + * + * Here we manipulate the fields in order of the AArch32 SPSR_ELx layout, from + * MSB to LSB. + */ +static unsigned long get_except32_cpsr(struct kvm_vcpu *vcpu, u32 mode) +{ + u32 sctlr = vcpu_cp15(vcpu, c1_SCTLR); + unsigned long old, new; + + old = *vcpu_cpsr(vcpu); + new = 0; + + new |= (old & PSR_AA32_N_BIT); + new |= (old & PSR_AA32_Z_BIT); + new |= (old & PSR_AA32_C_BIT); + new |= (old & PSR_AA32_V_BIT); + new |= (old & PSR_AA32_Q_BIT); + + // CPSR.IT[7:0] are set to zero upon any exception + // See ARM DDI 0487E.a, section G1.12.3 + // See ARM DDI 0406C.d, section B1.8.3 + + new |= (old & PSR_AA32_DIT_BIT); + + // CPSR.SSBS is set to SCTLR.DSSBS upon any exception + // See ARM DDI 0487E.a, page G8-6244 + if (sctlr & BIT(31)) + new |= PSR_AA32_SSBS_BIT; + + // CPSR.PAN is unchanged unless overridden by SCTLR.SPAN + // See ARM DDI 0487E.a, page G8-6246 + new |= (old & PSR_AA32_PAN_BIT); + if (sctlr & BIT(23)) + new |= PSR_AA32_PAN_BIT; + + // SS does not exist in AArch32, so ignore + + // CPSR.IL is set to zero upon any exception + // See ARM DDI 0487E.a, page G1-5527 + + new |= (old & PSR_AA32_GE_MASK); + + // CPSR.IT[7:0] are set to zero upon any exception + // See prior comment above + + // CPSR.E is set to SCTLR.EE upon any exception + // See ARM DDI 0487E.a, page G8-6245 + // See ARM DDI 0406C.d, page B4-1701 + if (sctlr & BIT(25)) + new |= PSR_AA32_E_BIT; + + // CPSR.A is unchanged upon an exception to Undefined, Supervisor + // CPSR.A is set upon an exception to other modes + // See ARM DDI 0487E.a, pages G1-5515 to G1-5516 + // See ARM DDI 0406C.d, page B1-1182 + new |= (old & PSR_AA32_A_BIT); + if (mode != PSR_AA32_MODE_UND && mode != PSR_AA32_MODE_SVC) + new |= PSR_AA32_A_BIT; + + // CPSR.I is set upon any exception + // See ARM DDI 0487E.a, pages G1-5515 to G1-5516 + // See ARM DDI 0406C.d, page B1-1182 + new |= PSR_AA32_I_BIT; + + // CPSR.F is set upon an exception to FIQ + // CPSR.F is unchanged upon an exception to other modes + // See ARM DDI 0487E.a, pages G1-5515 to G1-5516 + // See ARM DDI 0406C.d, page B1-1182 + new |= (old & PSR_AA32_F_BIT); + if (mode == PSR_AA32_MODE_FIQ) + new |= PSR_AA32_F_BIT; + + // CPSR.T is set to SCTLR.TE upon any exception + // See ARM DDI 0487E.a, page G8-5514 + // See ARM DDI 0406C.d, page B1-1181 + if (sctlr & BIT(30)) + new |= PSR_AA32_T_BIT; + + new |= mode; + + return new; +} + static void prepare_fault32(struct kvm_vcpu *vcpu, u32 mode, u32 vect_offset) { - unsigned long cpsr; unsigned long new_spsr_value = *vcpu_cpsr(vcpu); bool is_thumb = (new_spsr_value & PSR_AA32_T_BIT); u32 return_offset = return_offsets[vect_offset >> 2][is_thumb]; u32 sctlr = vcpu_cp15(vcpu, c1_SCTLR);
- cpsr = mode | PSR_AA32_I_BIT; - - if (sctlr & (1 << 30)) - cpsr |= PSR_AA32_T_BIT; - if (sctlr & (1 << 25)) - cpsr |= PSR_AA32_E_BIT; - - *vcpu_cpsr(vcpu) = cpsr; + *vcpu_cpsr(vcpu) = get_except32_cpsr(vcpu, mode);
/* Note: These now point to the banked copies */ vcpu_write_spsr(vcpu, new_spsr_value); @@ -84,7 +174,7 @@ static void inject_abt32(struct kvm_vcpu *vcpu, bool is_pabt, fsr = &vcpu_cp15(vcpu, c5_DFSR); }
- prepare_fault32(vcpu, PSR_AA32_MODE_ABT | PSR_AA32_A_BIT, vect_offset); + prepare_fault32(vcpu, PSR_AA32_MODE_ABT, vect_offset);
*far = addr;
Hi,
On 12/20/19 3:05 PM, Mark Rutland wrote:
When KVM injects an exception into a guest, it generates the CPSR value from scratch, configuring CPSR.{M,A,I,T,E}, and setting all other bits to zero.
This isn't correct, as the architecture specifies that some CPSR bits are (conditionally) cleared or set upon an exception, and others are unchanged from the original context.
This patch adds logic to match the architectural behaviour. To make this simple to follow/audit/extend, documentation references are provided, and bits are configured in order of their layout in SPSR_EL2. This
This patch applies equally well to 32bit KVM, where we have a SPSR register.
layout can be seen in the diagram on ARM DDI 0487E.a page C5-426.
Signed-off-by: Mark Rutland mark.rutland@arm.com Cc: Alexandru Elisei alexandru.elisei@arm.com Cc: Drew Jones drjones@redhat.com Cc: James Morse james.morse@arm.com Cc: Julien Thierry julien.thierry.kdev@gmail.com Cc: Marc Zyngier maz@kernel.org Cc: Peter Maydell peter.maydell@linaro.org Cc: Suzuki K Poulose suzuki.poulose@arm.com Cc: Will Deacon will@kernel.org Cc: stable@vger.kernel.org
arch/arm/include/asm/kvm_emulate.h | 12 ++++ arch/arm64/include/asm/ptrace.h | 1 + virt/kvm/arm/aarch32.c | 110 +++++++++++++++++++++++++++++++++---- 3 files changed, 113 insertions(+), 10 deletions(-)
diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h index 40002416efec..dee2567661ed 100644 --- a/arch/arm/include/asm/kvm_emulate.h +++ b/arch/arm/include/asm/kvm_emulate.h @@ -14,13 +14,25 @@ #include <asm/cputype.h> /* arm64 compatibility macros */ +#define PSR_AA32_MODE_FIQ FIQ_MODE +#define PSR_AA32_MODE_SVC SVC_MODE #define PSR_AA32_MODE_ABT ABT_MODE #define PSR_AA32_MODE_UND UND_MODE #define PSR_AA32_T_BIT PSR_T_BIT +#define PSR_AA32_F_BIT PSR_F_BIT #define PSR_AA32_I_BIT PSR_I_BIT #define PSR_AA32_A_BIT PSR_A_BIT #define PSR_AA32_E_BIT PSR_E_BIT #define PSR_AA32_IT_MASK PSR_IT_MASK +#define PSR_AA32_GE_MASK 0x000f0000 +#define PSR_AA32_PAN_BIT 0x00400000 +#define PSR_AA32_SSBS_BIT 0x00800000 +#define PSR_AA32_DIT_BIT 0x01000000
This is actually PSR_J_BIT on arm. Maybe it's worth defining it like that to make the overlap obvious.
+#define PSR_AA32_Q_BIT PSR_Q_BIT +#define PSR_AA32_V_BIT PSR_V_BIT +#define PSR_AA32_C_BIT PSR_C_BIT +#define PSR_AA32_Z_BIT PSR_Z_BIT +#define PSR_AA32_N_BIT PSR_N_BIT unsigned long *vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num); diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index fbebb411ae20..bf57308fcd63 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -62,6 +62,7 @@ #define PSR_AA32_I_BIT 0x00000080 #define PSR_AA32_A_BIT 0x00000100 #define PSR_AA32_E_BIT 0x00000200 +#define PSR_AA32_PAN_BIT 0x00400000 #define PSR_AA32_SSBS_BIT 0x00800000 #define PSR_AA32_DIT_BIT 0x01000000 #define PSR_AA32_Q_BIT 0x08000000 diff --git a/virt/kvm/arm/aarch32.c b/virt/kvm/arm/aarch32.c index c4c57ba99e90..17bcde5c2451 100644 --- a/virt/kvm/arm/aarch32.c +++ b/virt/kvm/arm/aarch32.c @@ -10,6 +10,7 @@
- Author: Christoffer Dall c.dall@virtualopensystems.com
*/ +#include <linux/bits.h> #include <linux/kvm_host.h> #include <asm/kvm_emulate.h> #include <asm/kvm_hyp.h> @@ -28,22 +29,111 @@ static const u8 return_offsets[8][2] = { [7] = { 4, 4 }, /* FIQ, unused */ }; +/*
- When an exception is taken, most CPSR fields are left unchanged in the
- handler. However, some are explicitly overridden (e.g. M[4:0]).
- The SPSR/SPSR_ELx layouts differ, and the below is intended to work with
- either format. Note: SPSR.J bit doesn't exist in SPSR_ELx, but this bit was
- obsoleted by the ARMv7 virtualization extensions and is RES0.
- For the SPSR layout seen from AArch32, see:
- ARM DDI 0406C.d, page B1-1148
- ARM DDI 0487E.a, page G8-6264
- For the SPSR_ELx layout for AArch32 seen from AArch64, see:
- ARM DDI 0487E.a, page C5-426
- Here we manipulate the fields in order of the AArch32 SPSR_ELx layout, from
- MSB to LSB.
- */
+static unsigned long get_except32_cpsr(struct kvm_vcpu *vcpu, u32 mode) +{
- u32 sctlr = vcpu_cp15(vcpu, c1_SCTLR);
- unsigned long old, new;
- old = *vcpu_cpsr(vcpu);
- new = 0;
- new |= (old & PSR_AA32_N_BIT);
- new |= (old & PSR_AA32_Z_BIT);
- new |= (old & PSR_AA32_C_BIT);
- new |= (old & PSR_AA32_V_BIT);
- new |= (old & PSR_AA32_Q_BIT);
- // CPSR.IT[7:0] are set to zero upon any exception
- // See ARM DDI 0487E.a, section G1.12.3
- // See ARM DDI 0406C.d, section B1.8.3
- new |= (old & PSR_AA32_DIT_BIT);
- // CPSR.SSBS is set to SCTLR.DSSBS upon any exception
- // See ARM DDI 0487E.a, page G8-6244
- if (sctlr & BIT(31))
new |= PSR_AA32_SSBS_BIT;- // CPSR.PAN is unchanged unless overridden by SCTLR.SPAN
- // See ARM DDI 0487E.a, page G8-6246
- new |= (old & PSR_AA32_PAN_BIT);
- if (sctlr & BIT(23))
new |= PSR_AA32_PAN_BIT;
PSTATE.PAN is unconditionally set when SCTLR.SPAN is clear.
- // SS does not exist in AArch32, so ignore
- // CPSR.IL is set to zero upon any exception
- // See ARM DDI 0487E.a, page G1-5527
- new |= (old & PSR_AA32_GE_MASK);
- // CPSR.IT[7:0] are set to zero upon any exception
- // See prior comment above
- // CPSR.E is set to SCTLR.EE upon any exception
- // See ARM DDI 0487E.a, page G8-6245
- // See ARM DDI 0406C.d, page B4-1701
- if (sctlr & BIT(25))
new |= PSR_AA32_E_BIT;- // CPSR.A is unchanged upon an exception to Undefined, Supervisor
- // CPSR.A is set upon an exception to other modes
- // See ARM DDI 0487E.a, pages G1-5515 to G1-5516
- // See ARM DDI 0406C.d, page B1-1182
- new |= (old & PSR_AA32_A_BIT);
- if (mode != PSR_AA32_MODE_UND && mode != PSR_AA32_MODE_SVC)
new |= PSR_AA32_A_BIT;- // CPSR.I is set upon any exception
- // See ARM DDI 0487E.a, pages G1-5515 to G1-5516
- // See ARM DDI 0406C.d, page B1-1182
- new |= PSR_AA32_I_BIT;
- // CPSR.F is set upon an exception to FIQ
- // CPSR.F is unchanged upon an exception to other modes
- // See ARM DDI 0487E.a, pages G1-5515 to G1-5516
- // See ARM DDI 0406C.d, page B1-1182
- new |= (old & PSR_AA32_F_BIT);
- if (mode == PSR_AA32_MODE_FIQ)
new |= PSR_AA32_F_BIT;- // CPSR.T is set to SCTLR.TE upon any exception
- // See ARM DDI 0487E.a, page G8-5514
- // See ARM DDI 0406C.d, page B1-1181
- if (sctlr & BIT(30))
new |= PSR_AA32_T_BIT;- new |= mode;
- return new;
+}
static void prepare_fault32(struct kvm_vcpu *vcpu, u32 mode, u32 vect_offset) {
- unsigned long cpsr; unsigned long new_spsr_value = *vcpu_cpsr(vcpu); bool is_thumb = (new_spsr_value & PSR_AA32_T_BIT); u32 return_offset = return_offsets[vect_offset >> 2][is_thumb]; u32 sctlr = vcpu_cp15(vcpu, c1_SCTLR);
- cpsr = mode | PSR_AA32_I_BIT;
- if (sctlr & (1 << 30))
cpsr |= PSR_AA32_T_BIT;- if (sctlr & (1 << 25))
cpsr |= PSR_AA32_E_BIT;- *vcpu_cpsr(vcpu) = cpsr;
- *vcpu_cpsr(vcpu) = get_except32_cpsr(vcpu, mode);
/* Note: These now point to the banked copies */ vcpu_write_spsr(vcpu, new_spsr_value); @@ -84,7 +174,7 @@ static void inject_abt32(struct kvm_vcpu *vcpu, bool is_pabt, fsr = &vcpu_cp15(vcpu, c5_DFSR); }
- prepare_fault32(vcpu, PSR_AA32_MODE_ABT | PSR_AA32_A_BIT, vect_offset);
- prepare_fault32(vcpu, PSR_AA32_MODE_ABT, vect_offset);
*far = addr;
I've also checked that the ARM documentation references match the code.
Thanks, Alex
On Fri, Dec 27, 2019 at 03:42:34PM +0000, Alexandru Elisei wrote:
Hi,
On 12/20/19 3:05 PM, Mark Rutland wrote:
When KVM injects an exception into a guest, it generates the CPSR value from scratch, configuring CPSR.{M,A,I,T,E}, and setting all other bits to zero.
This isn't correct, as the architecture specifies that some CPSR bits are (conditionally) cleared or set upon an exception, and others are unchanged from the original context.
This patch adds logic to match the architectural behaviour. To make this simple to follow/audit/extend, documentation references are provided, and bits are configured in order of their layout in SPSR_EL2. This
This patch applies equally well to 32bit KVM, where we have a SPSR register.
Indeed. The above wasn't intended to imply otherwise, but I'll add the following to make that clear:
| Note that this code is used by both arm and arm64, and is intended to | fuction with the SPSR_EL2 and SPSR_hyp layouts.
[...]
/* arm64 compatibility macros */ +#define PSR_AA32_MODE_FIQ FIQ_MODE +#define PSR_AA32_MODE_SVC SVC_MODE #define PSR_AA32_MODE_ABT ABT_MODE #define PSR_AA32_MODE_UND UND_MODE #define PSR_AA32_T_BIT PSR_T_BIT +#define PSR_AA32_F_BIT PSR_F_BIT #define PSR_AA32_I_BIT PSR_I_BIT #define PSR_AA32_A_BIT PSR_A_BIT #define PSR_AA32_E_BIT PSR_E_BIT #define PSR_AA32_IT_MASK PSR_IT_MASK +#define PSR_AA32_GE_MASK 0x000f0000 +#define PSR_AA32_PAN_BIT 0x00400000 +#define PSR_AA32_SSBS_BIT 0x00800000 +#define PSR_AA32_DIT_BIT 0x01000000
This is actually PSR_J_BIT on arm. Maybe it's worth defining it like that to make the overlap obvious.
Another bug! These are intended to match the SPSR_hyp view, where DIT is bit 21, and so this should be:
#define PSR_AA32_DIT_BIT 0x0x00200000
... placed immediately before the PAN bit.
We don't need a macro for the J bit as it was obsoleted and made RES0 by the ARMv7 virtualization extensions.
[...]
- // CPSR.PAN is unchanged unless overridden by SCTLR.SPAN
- // See ARM DDI 0487E.a, page G8-6246
- new |= (old & PSR_AA32_PAN_BIT);
- if (sctlr & BIT(23))
new |= PSR_AA32_PAN_BIT;PSTATE.PAN is unconditionally set when SCTLR.SPAN is clear.
Indeed, and this time the reference is explicit about that. :/
I've updated this to:
| // CPSR.PAN is unchanged unless SCTLR.SPAN == 0b0 | // SCTLR.SPAN is RES1 when ARMv8.1-PAN is not implemented | // See ARM DDI 0487E.a, page G8-6246 | new |= (old & PSR_AA32_PAN_BIT); | if (!(sctlr & BIT(23))) | new |= PSR_AA32_PAN_BIT;
[...]
I've also checked that the ARM documentation references match the code.
Thanks, your review is much appreciated!
Mark.
linux-stable-mirror@lists.linaro.org
-
Alexandru Elisei -
Mark Rutland