From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org
Subject: Re: [PATCH kvm-unit-tests] x86: add and use *_BIT constants for CR0, CR4, EFLAGS
Date: Tue, 26 Jul 2022 17:32:14 +0000 [thread overview]
Message-ID: <YuAlHgkpBZS0QJ5e@google.com> (raw)
In-Reply-To: <20220726151232.92584-1-pbonzini@redhat.com>
On Tue, Jul 26, 2022, Paolo Bonzini wrote:
> The "BIT" macro cannot be used in top-level assembly statements
> (it can be used in functions through the "i" constraint). To
> avoid having to hard-code EFLAGS.AC being bit 18, define the
> constants for CR0, CR4 and EFLAGS bits in terms of new macros
> for just the bit number.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
...
> diff --git a/x86/smap.c b/x86/smap.c
> index 0994c29..3f63ee1 100644
> --- a/x86/smap.c
> +++ b/x86/smap.c
> @@ -39,7 +39,7 @@ asm ("pf_tss:\n"
> #endif
> "add $"S", %"R "sp\n"
> #ifdef __x86_64__
> - "orl $" xstr(X86_EFLAGS_AC) ", 2*"S"(%"R "sp)\n" // set EFLAGS.AC and retry
I don't understand, this compiles cleanly on both gcc and clang, and generates the
correct code. What am I missing?
> + "orl $(1<<" xstr(X86_EFLAGS_AC_BIT) "), 2*"S"(%"R "sp)\n" // set EFLAGS.AC and retry
> #endif
> "iret"W" \n\t"
> "jmp pf_tss\n\t");
> --
> 2.36.1
>
next prev parent reply other threads:[~2022-07-26 17:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-26 15:12 [PATCH kvm-unit-tests] x86: add and use *_BIT constants for CR0, CR4, EFLAGS Paolo Bonzini
2022-07-26 17:32 ` Sean Christopherson [this message]
2022-07-27 6:04 ` Paolo Bonzini
2022-07-27 18:00 ` Sean Christopherson
2022-07-28 15:13 ` Paolo Bonzini
-- strict thread matches above, loose matches on Subject: below --
2022-07-26 17:35 Paolo Bonzini
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