linux-kernel - Re: [PATCH -v1.2] kvm/emulate: Fix SETcc emulation function offsets with SLS

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Message-ID: <8618FFB5-4029-4C8C-9982-B431F967D468@alien8.de>
Date:   Sun, 20 Mar 2022 14:17:08 +0000
From:   Boris Petkov <bp@...en8.de>
To:     Paolo Bonzini <pbonzini@...hat.com>
CC:     Peter Zijlstra <peterz@...radead.org>,
        Jamie Heilman <jamie@...ible.transient.net>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sean Christopherson <seanjc@...gle.com>, x86@...nel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH -v1.2] kvm/emulate: Fix SETcc emulation function offsets with SLS

On March 20, 2022 2:04:02 PM UTC, Paolo Bonzini <pbonzini@...hat.com> wrote:
>So this is what I squashed in:
>
>diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
>index f321abb9a4a8..e86d610dc6b7 100644
>--- a/arch/x86/kvm/emulate.c
>+++ b/arch/x86/kvm/emulate.c
>@@ -430,7 +430,19 @@ static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop);
>  
>  /* Special case for SETcc - 1 instruction per cc */
>  
>-#define SETCC_ALIGN	(4 * (1 + IS_ENABLED(CONFIG_SLS)))
>+/*
>+ * Depending on .config the SETcc functions look like:
>+ *
>+ * SETcc %al   [3 bytes]
>+ * RET         [1 byte]
>+ * INT3        [1 byte; CONFIG_SLS]
>+ *
>+ * Which gives possible sizes 4 or 5.  When rounded up to the
>+ * next power-of-two alignment they become 4 or 8.
>+ */
>+#define SETCC_LENGTH	(4 + IS_ENABLED(CONFIG_SLS))
>+#define SETCC_ALIGN	(4 << IS_ENABLED(CONFIG_SLS))
>+static_assert(SETCC_LENGTH <= SETCC_ALIGN);
>  
>  #define FOP_SETCC(op) \
>  	".align " __stringify(SETCC_ALIGN) " \n\t" \
>
>Paolo


Ack.

Thanks.

-- 
Sent from a small device: formatting sux and brevity is inevitable.