Messages in this thread Patch in this message | | | Date | Thu, 7 Feb 2019 11:18:46 +0100 | From | Peter Zijlstra <> | Subject | Re: [GIT PULL] x86/mm changes for v4.21 |
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On Wed, Feb 06, 2019 at 04:17:42PM -0800, Luck, Tony wrote:
> fe0937b24ff5 ("x86/mm/cpa: Fold cpa_flush_range() and cpa_flush_array() into a single cpa_flush() function")
Boris pointed me at this gem:
c7486104a5ce ("x86/mce: Fix set_mce_nospec() to avoid #GP fault")
(can I just revel at the pure awesome grossness of that)
But we then see my above commit having:
@@ -1732,11 +1685,6 @@ static int change_page_attr_set_clr(unsigned long *addr, int numpages, */ WARN_ON_ONCE(1); } - /* - * Save address for cache flush. *addr is modified in the call - * to __change_page_attr_set_clr() below. - */ - baddr = make_addr_canonical_again(*addr);
Where I clearly got distracted by that excellent comment..
So now the question is where to put it back in, I'm thinking this might want to be in __cpa_addr().
Something like so?
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 4f8972311a77..319b767484fb 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -230,6 +230,28 @@ static bool __cpa_pfn_in_highmap(unsigned long pfn) #endif +/* + * Machine check recovery code needs to change cache mode of poisoned + * pages to UC to avoid speculative access logging another error. But + * passing the address of the 1:1 mapping to set_memory_uc() is a fine + * way to encourage a speculative access. So we cheat and flip the top + * bit of the address. This works fine for the code that updates the + * page tables. But at the end of the process we need to flush the cache + * and the non-canonical address causes a #GP fault when used by the + * CLFLUSH instruction. + * + * But in the common case we already have a canonical address. This code + * will fix the top bit if needed and is a no-op otherwise. + */ +static inline unsigned long make_addr_canonical_again(unsigned long addr) +{ +#ifdef CONFIG_X86_64 + return (long)(addr << 1) >> 1; +#else + return addr; +#endif +} + static unsigned long __cpa_addr(struct cpa_data *cpa, unsigned long idx) { if (cpa->flags & CPA_PAGES_ARRAY) { @@ -244,7 +266,7 @@ static unsigned long __cpa_addr(struct cpa_data *cpa, unsigned long idx) if (cpa->flags & CPA_ARRAY) return cpa->vaddr[idx]; - return *cpa->vaddr + idx * PAGE_SIZE; + return make_addr_canonical_again(*cpa->vaddr + idx * PAGE_SIZE); } /* @@ -1627,29 +1649,6 @@ static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias) return ret; } -/* - * Machine check recovery code needs to change cache mode of poisoned - * pages to UC to avoid speculative access logging another error. But - * passing the address of the 1:1 mapping to set_memory_uc() is a fine - * way to encourage a speculative access. So we cheat and flip the top - * bit of the address. This works fine for the code that updates the - * page tables. But at the end of the process we need to flush the cache - * and the non-canonical address causes a #GP fault when used by the - * CLFLUSH instruction. - * - * But in the common case we already have a canonical address. This code - * will fix the top bit if needed and is a no-op otherwise. - */ -static inline unsigned long make_addr_canonical_again(unsigned long addr) -{ -#ifdef CONFIG_X86_64 - return (long)(addr << 1) >> 1; -#else - return addr; -#endif -} - - static int change_page_attr_set_clr(unsigned long *addr, int numpages, pgprot_t mask_set, pgprot_t mask_clr, int force_split, int in_flag,
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