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Re: [PATCH v2] pv32: Fix bogus cr2 on fault in emulation gate
- To: Teddy Astie <teddy.astie@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 22 May 2026 14:42:46 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Fri, 22 May 2026 12:42:56 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 22.05.2026 14:33, Teddy Astie wrote:
> __{put,get}_guest returns -EFAULT on access faults which causes
> the injected cr2 to be off by 14 bytes (as EFAULT is 14) which is
> incorrect.
>
> Fix the computation by relying on copy_{from,to}_guest_pv which
> reports the number of remaining bytes instead of a negative errno,
> such that we can compute the offset properly.
>
> Fixes: 70ad570b2799 ("x86/64: paravirt 32-on-64 call gate support")
> Signed-off-by: Teddy Astie <teddy.astie@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
preferably with ...
> --- a/xen/arch/x86/pv/emul-gate-op.c
> +++ b/xen/arch/x86/pv/emul-gate-op.c
> @@ -286,12 +286,14 @@ void pv_emulate_gate_op(struct cpu_user_regs *regs)
> if ( !jump )
> {
> unsigned int ss, esp, *stkp;
> + uint32_t value;
> int rc;
> #define push(item) do \
> { \
> + value = item; \
... (item) here. I think we're okay without, but let's play safe.
Likely can be adjusted by the committer.
Jan
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