Messages in this thread Patch in this message | | | Date | Fri, 18 Feb 2022 16:07:09 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v2] x86/mce: work around an erratum on fast string copy instructions. |
| |
On Thu, Feb 17, 2022 at 05:32:09PM -0800, Jue Wang wrote: > +static noinstr bool quirk_skylake_repmov(void) > +{ > + u64 mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS); > + u64 misc_enable = __rdmsr(MSR_IA32_MISC_ENABLE); > + > + /* > + * Apply the quirk only to local machine checks, i.e., no broadcast > + * sync is needed. > + */ > + if ((mcgstatus & MCG_STATUS_LMCES) && > + unlikely(misc_enable & MSR_IA32_MISC_ENABLE_FAST_STRING)) { > + u64 mc1_status = mce_rdmsrl(MSR_IA32_MCx_STATUS(1)); > + > + /* Check for a software-recoverable data fetch error. */ > + if ((mc1_status & > + (MCI_STATUS_VAL | MCI_STATUS_OVER | MCI_STATUS_UC | MCI_STATUS_EN | > + MCI_STATUS_ADDRV | MCI_STATUS_MISCV | MCI_STATUS_PCC | > + MCI_STATUS_AR | MCI_STATUS_S)) == > + (MCI_STATUS_VAL | MCI_STATUS_UC | MCI_STATUS_EN | > + MCI_STATUS_ADDRV | MCI_STATUS_MISCV | > + MCI_STATUS_AR | MCI_STATUS_S)) { > + misc_enable &= ~MSR_IA32_MISC_ENABLE_FAST_STRING; > + __wrmsr(MSR_IA32_MISC_ENABLE, > + (u32)misc_enable, (u32)(misc_enable >> 32));
"You're going to have to use the mce_{rd,wr}msrl() routines."
I actually really meant that.
And I went and simplified this a bit more so that it is more readable, diff ontop.
Also, Tony, I think the clearing of MCG_STATUS should happen last.
--- diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c index c1a41da99975..1741be9b9464 100644 --- a/arch/x86/kernel/cpu/mce/core.c +++ b/arch/x86/kernel/cpu/mce/core.c @@ -831,34 +831,35 @@ quirk_sandybridge_ifu(int bank, struct mce *m, struct pt_regs *regs) */ static noinstr bool quirk_skylake_repmov(void) { - u64 mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS); - u64 misc_enable = __rdmsr(MSR_IA32_MISC_ENABLE); + u64 mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS); + u64 misc_enable = mce_rdmsrl(MSR_IA32_MISC_ENABLE); + u64 mc1_status; /* * Apply the quirk only to local machine checks, i.e., no broadcast * sync is needed. */ - if ((mcgstatus & MCG_STATUS_LMCES) && - (misc_enable & MSR_IA32_MISC_ENABLE_FAST_STRING)) { - u64 mc1_status = mce_rdmsrl(MSR_IA32_MCx_STATUS(1)); - - /* Check for a software-recoverable data fetch error. */ - if ((mc1_status & - (MCI_STATUS_VAL | MCI_STATUS_OVER | MCI_STATUS_UC | MCI_STATUS_EN | - MCI_STATUS_ADDRV | MCI_STATUS_MISCV | MCI_STATUS_PCC | - MCI_STATUS_AR | MCI_STATUS_S)) == - (MCI_STATUS_VAL | MCI_STATUS_UC | MCI_STATUS_EN | - MCI_STATUS_ADDRV | MCI_STATUS_MISCV | - MCI_STATUS_AR | MCI_STATUS_S)) { - misc_enable &= ~MSR_IA32_MISC_ENABLE_FAST_STRING; - __wrmsr(MSR_IA32_MISC_ENABLE, - (u32)misc_enable, (u32)(misc_enable >> 32)); - mce_wrmsrl(MSR_IA32_MCG_STATUS, 0); - mce_wrmsrl(MSR_IA32_MCx_STATUS(1), 0); - pr_err_once("Errata detected, disable fast string copy instructions.\n"); - return true; - } + if (!(mcgstatus & MCG_STATUS_LMCES) || + !(misc_enable & MSR_IA32_MISC_ENABLE_FAST_STRING)) + return false; + + mc1_status = mce_rdmsrl(MSR_IA32_MCx_STATUS(1)); + + /* Check for a software-recoverable data fetch error. */ + if ((mc1_status & + (MCI_STATUS_VAL | MCI_STATUS_OVER | MCI_STATUS_UC | MCI_STATUS_EN | + MCI_STATUS_ADDRV | MCI_STATUS_MISCV | MCI_STATUS_PCC | + MCI_STATUS_AR | MCI_STATUS_S)) == + (MCI_STATUS_VAL | MCI_STATUS_UC | MCI_STATUS_EN | + MCI_STATUS_ADDRV | MCI_STATUS_MISCV | + MCI_STATUS_AR | MCI_STATUS_S)) { + misc_enable &= ~MSR_IA32_MISC_ENABLE_FAST_STRING; + mce_wrmsrl(MSR_IA32_MISC_ENABLE, misc_enable); + mce_wrmsrl(MSR_IA32_MCx_STATUS(1), 0); + pr_err_once("Erratum detected, disable fast string copy instructions.\n"); + return true; } + return false; } @@ -1432,7 +1433,7 @@ noinstr void do_machine_check(struct pt_regs *regs) return unexpected_machine_check(regs); if (mce_flags.skx_repmov_quirk && quirk_skylake_repmov()) - return; + goto clear; /* * Establish sequential order between the CPUs entering the machine @@ -1576,6 +1577,7 @@ noinstr void do_machine_check(struct pt_regs *regs) out: instrumentation_end(); +clear: mce_wrmsrl(MSR_IA32_MCG_STATUS, 0); } EXPORT_SYMBOL_GPL(do_machine_check); -- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
| |