[Qemu-devel] Re: [PATCH uq/master 2/2] MCE, unpoison memory address across reboot

[Huang Ying]

On Thu, 2011-01-13 at 17:01 +0800, Jan Kiszka wrote:
> Am 13.01.2011 09:34, 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.
> > 
> > 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.
> > 
> > This patch fixes this issue in QEMU 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 <address@hidden>
> > ---
> >  kvm.h             |    2 ++
> >  target-i386/kvm.c |   39 +++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 41 insertions(+)
> > 
> > --- a/target-i386/kvm.c
> > +++ b/target-i386/kvm.c
> > @@ -580,6 +580,42 @@ static int kvm_get_supported_msrs(void)
> >      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);
> > +
> > +void kvm_unpoison_all(void *param)
> 
> Minor nit: This can be static now.

In uq/master, it can be make static.  But in kvm/master, kvm_arch_init
is not compiled because of conditional compiling, so we will get warning
and error for unused symbol.  Should we consider kvm/master in this
patch?

> > +{
> > +    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(void)
> >  {
> >      uint64_t identity_base = 0xfffbc000;
> > @@ -632,6 +668,7 @@ int kvm_arch_init(void)
> >          fprintf(stderr, "e820_add_entry() table is full\n");
> >          return ret;
> >      }
> > +    qemu_register_reset(kvm_unpoison_all, NULL);
> >  
> >      return 0;
> >  }
> > @@ -1940,6 +1977,7 @@ int kvm_on_sigbus_vcpu(CPUState *env, in
> >                  hardware_memory_error();
> >              }
> >          }
> > +        kvm_hwpoison_page_add(ram_addr);
> >  
> >          if (code == BUS_MCEERR_AR) {
> >              /* Fake an Intel architectural Data Load SRAR UCR */
> > @@ -1984,6 +2022,7 @@ int kvm_on_sigbus(int code, void *addr)
> >                      "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
> > --- a/kvm.h
> > +++ b/kvm.h
> > @@ -188,6 +188,8 @@ int kvm_physical_memory_addr_from_ram(ra
> >                                        target_phys_addr_t *phys_addr);
> >  #endif
> >  
> > +void kvm_unpoison_all(void *param);
> > +
> 
> To be removed if kvm_unpoison_all is static.
> 
> >  #endif
> >  int kvm_set_ioeventfd_mmio_long(int fd, uint32_t adr, uint32_t val, bool 
> > assign);
> >  
> > 
> 
> As indicated, I'm sitting on lots of fixes and refactorings of the MCE
> user space code. How do you test your patches? Any suggestions how to do
> this efficiently would be warmly welcome.

We use a self-made test script to test.  Repository is at:

git://git.kernel.org/pub/scm/utils/cpu/mce/mce-test.git

The kvm test script is in kvm sub-directory.

The qemu patch attached is need by the test script.

Best Regards,
Huang Ying

p2v.patch
Description: Text Data