On 2011-02-09 04:00, Huang Ying wrote:
> In Linux kernel HWPoison processing implementation, the virtual
> address in processes mapping the error physical memory page is marked
> as HWPoison. So that, the further accessing to the virtual
> address will kill corresponding processes with SIGBUS.
>
> If the error physical memory page is used by a KVM guest, the SIGBUS
> will be sent to QEMU, and QEMU will simulate a MCE to report that
> memory error to the guest OS. If the guest OS can not recover from
> the error (for example, the page is accessed by kernel code), guest OS
> will reboot the system. But because the underlying host virtual
> address backing the guest physical memory is still poisoned, if the
> guest system accesses the corresponding guest physical memory even
> after rebooting, the SIGBUS will still be sent to QEMU and MCE will be
> simulated. That is, guest system can not recover via rebooting.
Yeah, saw this already during my test...
>
> In fact, across rebooting, the contents of guest physical memory page
> need not to be kept. We can allocate a new host physical page to
> back the corresponding guest physical address.
I just wondering what would be architecturally suboptimal if we simply
remapped on SIGBUS directly. Would save us at least the bookkeeping.
>
> This patch fixes this issue in QEMU-KVM via calling qemu_ram_remap()
> to clear the corresponding page table entry, so that make it possible
> to allocate a new page to recover the issue.
>
> Signed-off-by: Huang Ying <ying.huang@xxxxxxxxx>
> ---
> target-i386/kvm.c | 39 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 39 insertions(+)
>
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -508,6 +508,42 @@ static int kvm_get_supported_msrs(KVMSta
> return ret;
> }
>
> +struct HWPoisonPage;
> +typedef struct HWPoisonPage HWPoisonPage;
> +struct HWPoisonPage
> +{
> + ram_addr_t ram_addr;
> + QLIST_ENTRY(HWPoisonPage) list;
> +};
> +
> +static QLIST_HEAD(hwpoison_page_list, HWPoisonPage) hwpoison_page_list =
> + QLIST_HEAD_INITIALIZER(hwpoison_page_list);
> +
> +static void kvm_unpoison_all(void *param)
> +{
> + HWPoisonPage *page, *next_page;
> +
> + QLIST_FOREACH_SAFE(page, &hwpoison_page_list, list, next_page) {
> + QLIST_REMOVE(page, list);
> + qemu_ram_remap(page->ram_addr, TARGET_PAGE_SIZE);
> + qemu_free(page);
> + }
> +}
> +
> +static void kvm_hwpoison_page_add(ram_addr_t ram_addr)
> +{
> + HWPoisonPage *page;
> +
> + QLIST_FOREACH(page, &hwpoison_page_list, list) {
> + if (page->ram_addr == ram_addr)
> + return;
> + }
> +
> + page = qemu_malloc(sizeof(HWPoisonPage));
> + page->ram_addr = ram_addr;
> + QLIST_INSERT_HEAD(&hwpoison_page_list, page, list);
> +}
> +
> int kvm_arch_init(KVMState *s)
> {
> uint64_t identity_base = 0xfffbc000;
> @@ -556,6 +592,7 @@ int kvm_arch_init(KVMState *s)
> fprintf(stderr, "e820_add_entry() table is full\n");
> return ret;
> }
> + qemu_register_reset(kvm_unpoison_all, NULL);
>
> return 0;
> }
> @@ -1882,6 +1919,7 @@ int kvm_arch_on_sigbus_vcpu(CPUState *en
> hardware_memory_error();
> }
> }
> + kvm_hwpoison_page_add(ram_addr);
>
> if (code == BUS_MCEERR_AR) {
> /* Fake an Intel architectural Data Load SRAR UCR */
> @@ -1926,6 +1964,7 @@ int kvm_arch_on_sigbus(int code, void *a
> "QEMU itself instead of guest system!: %p\n", addr);
> return 0;
> }
> + kvm_hwpoison_page_add(ram_addr);
> kvm_mce_inj_srao_memscrub2(first_cpu, paddr);
> } else
> #endif
>
>
Looks fine otherwise. Unless that simplification makes sense, I could
offer to include this into my MCE rework (there is some minor conflict).
If all goes well, that series should be posted during this week.
Jan
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