Messages in this thread | | | Date | Mon, 13 Feb 2023 07:27:26 +0100 | Subject | Re: [PATCH v2 2/8] x86/mtrr: support setting MTRR state for software defined MTRRs | From | Juergen Gross <> |
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On 13.02.23 02:07, Michael Kelley (LINUX) wrote: > From: Juergen Gross <jgross@suse.com> Sent: Wednesday, February 8, 2023 11:22 PM >> >> When running virtualized, MTRR access can be reduced (e.g. in Xen PV >> guests or when running as a SEV-SNP guest under Hyper-V). Typically >> the hypervisor will reset the MTRR feature in cpuid data, resulting >> in no MTRR memory type information being available for the kernel. >> >> This has turned out to result in problems: >> >> - Hyper-V SEV-SNP guests using uncached mappings where they shouldn't >> - Xen PV dom0 mapping memory as WB which should be UC- instead >> >> Solve those problems by supporting to set a fixed MTRR state, >> overwriting the empty state used today. In case such a state has been >> set, don't call get_mtrr_state() in mtrr_bp_init(). The set state >> will only be used by mtrr_type_lookup(), as in all other cases >> mtrr_enabled() is being checked, which will return false. Accept the >> overwrite call only in case of MTRRs being disabled in cpuid. >> >> Signed-off-by: Juergen Gross <jgross@suse.com> >> --- >> V2: >> - new patch >> --- >> arch/x86/include/asm/mtrr.h | 2 ++ >> arch/x86/kernel/cpu/mtrr/generic.c | 38 ++++++++++++++++++++++++++++++ >> arch/x86/kernel/cpu/mtrr/mtrr.c | 9 +++++++ >> 3 files changed, 49 insertions(+) >> >> diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h >> index f0eeaf6e5f5f..0b8f51d683dc 100644 >> --- a/arch/x86/include/asm/mtrr.h >> +++ b/arch/x86/include/asm/mtrr.h >> @@ -31,6 +31,8 @@ >> */ >> # ifdef CONFIG_MTRR >> void mtrr_bp_init(void); >> +void mtrr_overwrite_state(struct mtrr_var_range *var, unsigned int num_var, >> + mtrr_type *fixed, mtrr_type def_type); > > Could you add a stub for the !CONFIG_MTRR case? Then the > #ifdef CONFIG_MTRR could be removed in Patch 3 of this series.
I was on the edge whether to add a stub. The Xen use case strongly suggests that the code wants to be inside an #ifdef, while the Hyper-V case is so simple, that it would benefit from the stub. As there was another #ifdef just above the added code in mshyperv.c I believed it would be fine without a stub. As you seem to like it better with the stub, I can add it.
Juergen [unhandled content-type:application/pgp-keys][unhandled content-type:application/pgp-signature] | |