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From foo@baz Tue Mar 8 07:37:56 PM CET 2022 |
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From: Kim Phillips <kim.phillips@amd.com> |
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Date: Mon, 28 Feb 2022 11:23:15 -0600 |
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Subject: x86/speculation: Use generic retpoline by default on AMD |
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From: Kim Phillips <kim.phillips@amd.com> |
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commit 244d00b5dd4755f8df892c86cab35fb2cfd4f14b upstream. |
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|
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AMD retpoline may be susceptible to speculation. The speculation |
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execution window for an incorrect indirect branch prediction using |
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LFENCE/JMP sequence may potentially be large enough to allow |
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exploitation using Spectre V2. |
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|
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By default, don't use retpoline,lfence on AMD. Instead, use the |
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generic retpoline. |
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|
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Signed-off-by: Kim Phillips <kim.phillips@amd.com> |
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Signed-off-by: Borislav Petkov <bp@suse.de> |
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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--- |
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arch/x86/kernel/cpu/bugs.c | 9 --------- |
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1 file changed, 9 deletions(-) |
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|
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--- a/arch/x86/kernel/cpu/bugs.c |
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+++ b/arch/x86/kernel/cpu/bugs.c |
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@@ -941,15 +941,6 @@ static enum spectre_v2_mitigation __init |
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return SPECTRE_V2_NONE; |
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} |
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|
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- if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || |
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- boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) { |
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- if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) { |
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- pr_err("LFENCE not serializing, switching to generic retpoline\n"); |
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- return SPECTRE_V2_RETPOLINE; |
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- } |
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- return SPECTRE_V2_LFENCE; |
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- } |
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- |
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return SPECTRE_V2_RETPOLINE; |
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} |
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