From: Roman Bolshakov <roman@roolebo.dev>
To: Phil Dennis-Jordan <phil@philjordan.eu>
Cc: qemu-devel@nongnu.org, dirty@apple.com, rbolshakov@ddn.com,
pbonzini@redhat.com
Subject: Re: [PATCH 2/5] i386/hvf: Fix for UB in handling CPUID function 0xD
Date: Wed, 6 Nov 2024 21:01:45 +0700 [thread overview]
Message-ID: <Zyt2yWzbJirnxPOb@roolebo.dev> (raw)
In-Reply-To: <20241105155800.5461-3-phil@philjordan.eu>
On Tue, Nov 05, 2024 at 04:57:57PM +0100, Phil Dennis-Jordan wrote:
> The handling for CPUID function 0xD (supported XSAVE features) was
> improved in a recent patch. Unfortunately, this appears to have
> introduced undefined behaviour for cases where ecx > 30, as the result
> of (1 << idx) is undefined if idx > 30.
>
> Per Intel SDM section 13.2, the behaviour for ecx values up to and
> including 62 are specified. This change therefore specifically sets
> all registers returned by the CPUID instruction to 0 for 63 and higher.
> Furthermore, the bit shift uses uint64_t, where behaviour for the entire
> range of 2..62 is safe and correct.
>
Thanks for correcting the regression.
Reviewed-by: Roman Bolshakov <rbolshakov@ddn.com>
next prev parent reply other threads:[~2024-11-06 14:02 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-05 15:57 [PATCH 0/5] i386/hvf: x2apic support and some small fixes Phil Dennis-Jordan
2024-11-05 15:57 ` [PATCH 1/5] i386/hvf: Integrates x2APIC support with hvf accel Phil Dennis-Jordan
2024-11-06 10:44 ` Roman Bolshakov
2024-11-05 15:57 ` [PATCH 2/5] i386/hvf: Fix for UB in handling CPUID function 0xD Phil Dennis-Jordan
2024-11-06 14:01 ` Roman Bolshakov [this message]
2024-11-05 15:57 ` [PATCH 3/5] i386/hvf: Fixes startup memory leak (vmcs caps) Phil Dennis-Jordan
2024-11-06 14:03 ` Roman Bolshakov
2024-11-05 15:57 ` [PATCH 4/5] i386/hvf: Raise exception on error setting APICBASE Phil Dennis-Jordan
2024-11-06 14:04 ` Roman Bolshakov
2024-11-05 15:58 ` [PATCH 5/5] i386/hvf: Removes duplicate/shadowed variables in hvf_vcpu_exec Phil Dennis-Jordan
2024-11-06 14:05 ` Roman Bolshakov
2024-11-06 15:26 ` [PATCH 0/5] i386/hvf: x2apic support and some small fixes Roman Bolshakov
2024-11-06 18:45 ` Phil Dennis-Jordan
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