On Wed, Sep 11, 2024 at 02:08:47PM +0200, Alexey Gladkov wrote:
On Tue, Sep 10, 2024 at 12:54:19PM -0700, Dave Hansen wrote:
On 9/6/24 04:49, Alexey Gladkov wrote:
+static inline bool is_kernel_addr(unsigned long addr) +{
- return (long)addr < 0;
+}
static int handle_mmio(struct pt_regs *regs, struct ve_info *ve) { unsigned long *reg, val, vaddr; @@ -434,6 +439,11 @@ static int handle_mmio(struct pt_regs *regs, struct ve_info *ve) return -EINVAL; }
- if (!user_mode(regs) && !is_kernel_addr(ve->gla)) {
WARN_ONCE(1, "Access to userspace address is not supported");return -EINVAL;- }
Should we really be open-coding a "is_kernel_addr" check? I mean, TASK_SIZE_MAX is there for a reason. While I doubt we'd ever change the positive vs. negative address space convention on 64-bit, I don't see a good reason to write a 64-bit x86-specific is_kernel_addr() when a more generic, portable and conventional idiom would do.
I took arch/x86/events/perf_event.h:1262 as an example. There is no special reason in its own function.
So, please use either a:
addr < TASK_SIZE_MAX
check, or use fault_in_kernel_space() directly.
I'll use fault_in_kernel_space() since SEV uses it. Thanks.
Also user_mode() check is redundant until later in the patchset. Move it to the patch that allows userspace MMIO.