| Message ID | 20220422224508.440670-4-jane.chu@oracle.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | e4628f04a31a3c3e03364a16bbfac0f07ad02b40 |
| Headers | show |
| Series | DAX poison recovery | expand |
[ Add Tony as the originator of the whole_page() logic and Jue who
reported the issue that lead to 17fae1294ad9 x86/{mce,mm}: Unmap the
entire page if the whole page is affected and poisoned ]
On Fri, Apr 22, 2022 at 3:46 PM Jane Chu <jane.chu@oracle.com> wrote:
>
> The set_memory_uc() approach doesn't work well in all cases.
> As Dan pointed out when "The VMM unmapped the bad page from
> guest physical space and passed the machine check to the guest."
> "The guest gets virtual #MC on an access to that page. When
> the guest tries to do set_memory_uc() and instructs cpa_flush()
> to do clean caches that results in taking another fault / exception
> perhaps because the VMM unmapped the page from the guest."
>
> Since the driver has special knowledge to handle NP or UC,
> mark the poisoned page with NP and let driver handle it when
> it comes down to repair.
>
> Please refer to discussions here for more details.
> https://lore.kernel.org/all/CAPcyv4hrXPb1tASBZUg-GgdVs0OOFKXMXLiHmktg_kFi7YBMyQ@mail.gmail.com/
>
> Now since poisoned page is marked as not-present, in order to
> avoid writing to a not-present page and trigger kernel Oops,
> also fix pmem_do_write().
>
> Fixes: 284ce4011ba6 ("x86/memory_failure: Introduce {set, clear}_mce_nospec()")
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Jane Chu <jane.chu@oracle.com>
> ---
> arch/x86/kernel/cpu/mce/core.c | 6 +++---
> arch/x86/mm/pat/set_memory.c | 23 +++++++++++------------
> drivers/nvdimm/pmem.c | 30 +++++++-----------------------
> include/linux/set_memory.h | 4 ++--
> 4 files changed, 23 insertions(+), 40 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> index 981496e6bc0e..fa67bb9d1afe 100644
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -579,7 +579,7 @@ static int uc_decode_notifier(struct notifier_block *nb, unsigned long val,
>
> pfn = mce->addr >> PAGE_SHIFT;
> if (!memory_failure(pfn, 0)) {
> - set_mce_nospec(pfn, whole_page(mce));
> + set_mce_nospec(pfn);
> mce->kflags |= MCE_HANDLED_UC;
> }
>
> @@ -1316,7 +1316,7 @@ static void kill_me_maybe(struct callback_head *cb)
>
> ret = memory_failure(p->mce_addr >> PAGE_SHIFT, flags);
> if (!ret) {
> - set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
> + set_mce_nospec(p->mce_addr >> PAGE_SHIFT);
> sync_core();
> return;
> }
> @@ -1342,7 +1342,7 @@ static void kill_me_never(struct callback_head *cb)
> p->mce_count = 0;
> pr_err("Kernel accessed poison in user space at %llx\n", p->mce_addr);
> if (!memory_failure(p->mce_addr >> PAGE_SHIFT, 0))
> - set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
> + set_mce_nospec(p->mce_addr >> PAGE_SHIFT);
> }
>
> static void queue_task_work(struct mce *m, char *msg, void (*func)(struct callback_head *))
> diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
> index 978cf5bd2ab6..e3a5e55f3e08 100644
> --- a/arch/x86/mm/pat/set_memory.c
> +++ b/arch/x86/mm/pat/set_memory.c
> @@ -1925,13 +1925,8 @@ int set_memory_wb(unsigned long addr, int numpages)
> }
> EXPORT_SYMBOL(set_memory_wb);
>
> -/*
> - * Prevent speculative access to the page by either unmapping
> - * it (if we do not require access to any part of the page) or
> - * marking it uncacheable (if we want to try to retrieve data
> - * from non-poisoned lines in the page).
> - */
> -int set_mce_nospec(unsigned long pfn, bool unmap)
> +/* Prevent speculative access to a page by marking it not-present */
> +int set_mce_nospec(unsigned long pfn)
> {
> unsigned long decoy_addr;
> int rc;
> @@ -1956,19 +1951,23 @@ int set_mce_nospec(unsigned long pfn, bool unmap)
> */
> decoy_addr = (pfn << PAGE_SHIFT) + (PAGE_OFFSET ^ BIT(63));
>
> - if (unmap)
> - rc = set_memory_np(decoy_addr, 1);
> - else
> - rc = set_memory_uc(decoy_addr, 1);
> + rc = set_memory_np(decoy_addr, 1);
> if (rc)
> pr_warn("Could not invalidate pfn=0x%lx from 1:1 map\n", pfn);
> return rc;
> }
>
> +static int set_memory_present(unsigned long *addr, int numpages)
> +{
> + return change_page_attr_set(addr, numpages, __pgprot(_PAGE_PRESENT), 0);
> +}
> +
> /* Restore full speculative operation to the pfn. */
> int clear_mce_nospec(unsigned long pfn)
> {
> - return set_memory_wb((unsigned long) pfn_to_kaddr(pfn), 1);
> + unsigned long addr = (unsigned long) pfn_to_kaddr(pfn);
> +
> + return set_memory_present(&addr, 1);
> }
> EXPORT_SYMBOL_GPL(clear_mce_nospec);
>
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index 58d95242a836..4aa17132a557 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -158,36 +158,20 @@ static blk_status_t pmem_do_write(struct pmem_device *pmem,
> struct page *page, unsigned int page_off,
> sector_t sector, unsigned int len)
> {
> - blk_status_t rc = BLK_STS_OK;
> - bool bad_pmem = false;
> phys_addr_t pmem_off = sector * 512 + pmem->data_offset;
> void *pmem_addr = pmem->virt_addr + pmem_off;
>
> - if (unlikely(is_bad_pmem(&pmem->bb, sector, len)))
> - bad_pmem = true;
> + if (unlikely(is_bad_pmem(&pmem->bb, sector, len))) {
> + blk_status_t rc = pmem_clear_poison(pmem, pmem_off, len);
> +
> + if (rc != BLK_STS_OK)
> + return rc;
> + }
>
> - /*
> - * Note that we write the data both before and after
> - * clearing poison. The write before clear poison
> - * handles situations where the latest written data is
> - * preserved and the clear poison operation simply marks
> - * the address range as valid without changing the data.
> - * In this case application software can assume that an
> - * interrupted write will either return the new good
> - * data or an error.
> - *
> - * However, if pmem_clear_poison() leaves the data in an
> - * indeterminate state we need to perform the write
> - * after clear poison.
> - */
> flush_dcache_page(page);
> write_pmem(pmem_addr, page, page_off, len);
> - if (unlikely(bad_pmem)) {
> - rc = pmem_clear_poison(pmem, pmem_off, len);
> - write_pmem(pmem_addr, page, page_off, len);
> - }
>
> - return rc;
> + return BLK_STS_OK;
> }
>
> static void pmem_submit_bio(struct bio *bio)
> diff --git a/include/linux/set_memory.h b/include/linux/set_memory.h
> index 683a6c3f7179..369769ce7399 100644
> --- a/include/linux/set_memory.h
> +++ b/include/linux/set_memory.h
> @@ -43,10 +43,10 @@ static inline bool can_set_direct_map(void)
> #endif /* CONFIG_ARCH_HAS_SET_DIRECT_MAP */
>
> #ifdef CONFIG_X86_64
> -int set_mce_nospec(unsigned long pfn, bool unmap);
> +int set_mce_nospec(unsigned long pfn);
> int clear_mce_nospec(unsigned long pfn);
> #else
> -static inline int set_mce_nospec(unsigned long pfn, bool unmap)
> +static inline int set_mce_nospec(unsigned long pfn)
> {
> return 0;
> }
> --
> 2.18.4
>
On Fri, Apr 22, 2022 at 4:25 PM Dan Williams <dan.j.williams@intel.com> wrote: > > [ Add Tony as the originator of the whole_page() logic and Jue who > reported the issue that lead to 17fae1294ad9 x86/{mce,mm}: Unmap the > entire page if the whole page is affected and poisoned ] > > > On Fri, Apr 22, 2022 at 3:46 PM Jane Chu <jane.chu@oracle.com> wrote: > > > > The set_memory_uc() approach doesn't work well in all cases. > > As Dan pointed out when "The VMM unmapped the bad page from > > guest physical space and passed the machine check to the guest." > > "The guest gets virtual #MC on an access to that page. When > > the guest tries to do set_memory_uc() and instructs cpa_flush() > > to do clean caches that results in taking another fault / exception > > perhaps because the VMM unmapped the page from the guest." > > > > Since the driver has special knowledge to handle NP or UC, > > mark the poisoned page with NP and let driver handle it when > > it comes down to repair. > > > > Please refer to discussions here for more details. > > https://lore.kernel.org/all/CAPcyv4hrXPb1tASBZUg-GgdVs0OOFKXMXLiHmktg_kFi7YBMyQ@mail.gmail.com/ > > > > Now since poisoned page is marked as not-present, in order to > > avoid writing to a not-present page and trigger kernel Oops, > > also fix pmem_do_write(). > > > > Fixes: 284ce4011ba6 ("x86/memory_failure: Introduce {set, clear}_mce_nospec()") > > Reviewed-by: Christoph Hellwig <hch@lst.de> > > Reviewed-by: Dan Williams <dan.j.williams@intel.com> > > Signed-off-by: Jane Chu <jane.chu@oracle.com> Boris, This is the last patch in this set that needs an x86 maintainer ack. Since you have been involved in the history for most of this, mind giving it an ack so I can pull it in for v5.19? Let me know if you want a resend.
On Tue, May 10, 2022 at 08:56:21PM -0700, Dan Williams wrote: > This is the last patch in this set that needs an x86 maintainer ack. > Since you have been involved in the history for most of this, mind > giving it an ack so I can pull it in for v5.19? Let me know if you > want a resend. I - just like you - am waiting for Tony to say whether he still needs this whole_page() thing. I already suggested removing it so I'm fine with this patch.
> I - just like you - am waiting for Tony to say whether he still needs > this whole_page() thing. I already suggested removing it so I'm fine > with this patch. IIRC this new patch effectively reverts back to the original behavior that I implemented back at the dawn of time. I.e. just always mark the whole page "not present" and don't try to mess with UC mappings to allow partial (but non-speculative) access to the not-poisoned parts of the page. If that is the case ... then Acked-by: Tony Luck <tony.luck@intel.com> If I've misunderstood ... then please explain what it is doing. Thanks -Tony
On Wed, May 11, 2022 at 10:17 AM Luck, Tony <tony.luck@intel.com> wrote: > > > I - just like you - am waiting for Tony to say whether he still needs > > this whole_page() thing. I already suggested removing it so I'm fine > > with this patch. > > IIRC this new patch effectively reverts back to the original behavior that > I implemented back at the dawn of time. I.e. just always mark the whole > page "not present" and don't try to mess with UC mappings to allow > partial (but non-speculative) access to the not-poisoned parts of the > page. > > If that is the case ... then Acked-by: Tony Luck <tony.luck@intel.com> > > If I've misunderstood ... then please explain what it is doing. You are correct. The page is always marked not present as far as the page-offlining code is concerned, back to the way it always was. The code in the pmem driver that repairs the page now knows that the page is to be kept "not present" until the poison is cleared and clear_mce_nospec() returns the mapping to typical write-back caching. There is no support for what the UC case previously allowed which was reading the good lines around the one bad line, just handle overwrites to clear poison and restore access.
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c index 981496e6bc0e..fa67bb9d1afe 100644 --- a/arch/x86/kernel/cpu/mce/core.c +++ b/arch/x86/kernel/cpu/mce/core.c @@ -579,7 +579,7 @@ static int uc_decode_notifier(struct notifier_block *nb, unsigned long val, pfn = mce->addr >> PAGE_SHIFT; if (!memory_failure(pfn, 0)) { - set_mce_nospec(pfn, whole_page(mce)); + set_mce_nospec(pfn); mce->kflags |= MCE_HANDLED_UC; } @@ -1316,7 +1316,7 @@ static void kill_me_maybe(struct callback_head *cb) ret = memory_failure(p->mce_addr >> PAGE_SHIFT, flags); if (!ret) { - set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page); + set_mce_nospec(p->mce_addr >> PAGE_SHIFT); sync_core(); return; } @@ -1342,7 +1342,7 @@ static void kill_me_never(struct callback_head *cb) p->mce_count = 0; pr_err("Kernel accessed poison in user space at %llx\n", p->mce_addr); if (!memory_failure(p->mce_addr >> PAGE_SHIFT, 0)) - set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page); + set_mce_nospec(p->mce_addr >> PAGE_SHIFT); } static void queue_task_work(struct mce *m, char *msg, void (*func)(struct callback_head *)) diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c index 978cf5bd2ab6..e3a5e55f3e08 100644 --- a/arch/x86/mm/pat/set_memory.c +++ b/arch/x86/mm/pat/set_memory.c @@ -1925,13 +1925,8 @@ int set_memory_wb(unsigned long addr, int numpages) } EXPORT_SYMBOL(set_memory_wb); -/* - * Prevent speculative access to the page by either unmapping - * it (if we do not require access to any part of the page) or - * marking it uncacheable (if we want to try to retrieve data - * from non-poisoned lines in the page). - */ -int set_mce_nospec(unsigned long pfn, bool unmap) +/* Prevent speculative access to a page by marking it not-present */ +int set_mce_nospec(unsigned long pfn) { unsigned long decoy_addr; int rc; @@ -1956,19 +1951,23 @@ int set_mce_nospec(unsigned long pfn, bool unmap) */ decoy_addr = (pfn << PAGE_SHIFT) + (PAGE_OFFSET ^ BIT(63)); - if (unmap) - rc = set_memory_np(decoy_addr, 1); - else - rc = set_memory_uc(decoy_addr, 1); + rc = set_memory_np(decoy_addr, 1); if (rc) pr_warn("Could not invalidate pfn=0x%lx from 1:1 map\n", pfn); return rc; } +static int set_memory_present(unsigned long *addr, int numpages) +{ + return change_page_attr_set(addr, numpages, __pgprot(_PAGE_PRESENT), 0); +} + /* Restore full speculative operation to the pfn. */ int clear_mce_nospec(unsigned long pfn) { - return set_memory_wb((unsigned long) pfn_to_kaddr(pfn), 1); + unsigned long addr = (unsigned long) pfn_to_kaddr(pfn); + + return set_memory_present(&addr, 1); } EXPORT_SYMBOL_GPL(clear_mce_nospec); diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c index 58d95242a836..4aa17132a557 100644 --- a/drivers/nvdimm/pmem.c +++ b/drivers/nvdimm/pmem.c @@ -158,36 +158,20 @@ static blk_status_t pmem_do_write(struct pmem_device *pmem, struct page *page, unsigned int page_off, sector_t sector, unsigned int len) { - blk_status_t rc = BLK_STS_OK; - bool bad_pmem = false; phys_addr_t pmem_off = sector * 512 + pmem->data_offset; void *pmem_addr = pmem->virt_addr + pmem_off; - if (unlikely(is_bad_pmem(&pmem->bb, sector, len))) - bad_pmem = true; + if (unlikely(is_bad_pmem(&pmem->bb, sector, len))) { + blk_status_t rc = pmem_clear_poison(pmem, pmem_off, len); + + if (rc != BLK_STS_OK) + return rc; + } - /* - * Note that we write the data both before and after - * clearing poison. The write before clear poison - * handles situations where the latest written data is - * preserved and the clear poison operation simply marks - * the address range as valid without changing the data. - * In this case application software can assume that an - * interrupted write will either return the new good - * data or an error. - * - * However, if pmem_clear_poison() leaves the data in an - * indeterminate state we need to perform the write - * after clear poison. - */ flush_dcache_page(page); write_pmem(pmem_addr, page, page_off, len); - if (unlikely(bad_pmem)) { - rc = pmem_clear_poison(pmem, pmem_off, len); - write_pmem(pmem_addr, page, page_off, len); - } - return rc; + return BLK_STS_OK; } static void pmem_submit_bio(struct bio *bio) diff --git a/include/linux/set_memory.h b/include/linux/set_memory.h index 683a6c3f7179..369769ce7399 100644 --- a/include/linux/set_memory.h +++ b/include/linux/set_memory.h @@ -43,10 +43,10 @@ static inline bool can_set_direct_map(void) #endif /* CONFIG_ARCH_HAS_SET_DIRECT_MAP */ #ifdef CONFIG_X86_64 -int set_mce_nospec(unsigned long pfn, bool unmap); +int set_mce_nospec(unsigned long pfn); int clear_mce_nospec(unsigned long pfn); #else -static inline int set_mce_nospec(unsigned long pfn, bool unmap) +static inline int set_mce_nospec(unsigned long pfn) { return 0; }
The set_memory_uc() approach doesn't work well in all cases. As Dan pointed out when "The VMM unmapped the bad page from guest physical space and passed the machine check to the guest." "The guest gets virtual #MC on an access to that page. When the guest tries to do set_memory_uc() and instructs cpa_flush() to do clean caches that results in taking another fault / exception perhaps because the VMM unmapped the page from the guest." Since the driver has special knowledge to handle NP or UC, mark the poisoned page with NP and let driver handle it when it comes down to repair. Please refer to discussions here for more details. https://lore.kernel.org/all/CAPcyv4hrXPb1tASBZUg-GgdVs0OOFKXMXLiHmktg_kFi7YBMyQ@mail.gmail.com/ Now since poisoned page is marked as not-present, in order to avoid writing to a not-present page and trigger kernel Oops, also fix pmem_do_write(). Fixes: 284ce4011ba6 ("x86/memory_failure: Introduce {set, clear}_mce_nospec()") Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Jane Chu <jane.chu@oracle.com> --- arch/x86/kernel/cpu/mce/core.c | 6 +++--- arch/x86/mm/pat/set_memory.c | 23 +++++++++++------------ drivers/nvdimm/pmem.c | 30 +++++++----------------------- include/linux/set_memory.h | 4 ++-- 4 files changed, 23 insertions(+), 40 deletions(-)