[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH RFC 1/4] xen PVonHVM: use E820_Reserved area for shared_info
On 15/07/14 14:40, Vitaly Kuznetsov wrote: > From: Olaf Hering <olaf@xxxxxxxxx> > > This is a respin of 00e37bdb0113a98408de42db85be002f21dbffd3 > ("xen PVonHVM: move shared_info to MMIO before kexec"). > > Currently kexec in a PVonHVM guest fails with a triple fault because the > new kernel overwrites the shared info page. The exact failure depends on > the size of the kernel image. This patch moves the pfn from RAM into an > E820 reserved memory area. > > The pfn containing the shared_info is located somewhere in RAM. This will > cause trouble if the current kernel is doing a kexec boot into a new > kernel. The new kernel (and its startup code) can not know where the pfn > is, so it can not reserve the page. The hypervisor will continue to update > the pfn, and as a result memory corruption occours in the new kernel. > > The toolstack marks the memory area FC000000-FFFFFFFF as reserved in the > E820 map. Within that range newer toolstacks (4.3+) will keep 1MB > starting from FE700000 as reserved for guest use. Older Xen4 toolstacks > will usually not allocate areas up to FE700000, so FE700000 is expected > to work also with older toolstacks. > > In Xen3 there is no reserved area at a fixed location. If the guest is > started on such old hosts the shared_info page will be placed in RAM. As > a result kexec can not be used. > > Signed-off-by: Olaf Hering <olaf@xxxxxxxxx> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> > (cherry picked from commit 9d02b43dee0d7fb18dfb13a00915550b1a3daa9f) Is this a useful commit to give? Isn't it one of Konrad's random trees? > --- a/arch/x86/xen/enlighten.c > +++ b/arch/x86/xen/enlighten.c > @@ -1726,23 +1726,29 @@ asmlinkage __visible void __init > xen_start_kernel(void) > #endif > } > > -void __ref xen_hvm_init_shared_info(void) > +#ifdef CONFIG_XEN_PVHVM > +#define HVM_SHARED_INFO_ADDR 0xFE700000UL I would like clearer documentation for this magic address. Perhaps referring to some toolstack documentation? > @@ -1828,10 +1853,23 @@ static void __init xen_hvm_guest_init(void) > > static uint32_t __init xen_hvm_platform(void) > { > + uint32_t eax, ebx, ecx, edx, base; > + > if (xen_pv_domain()) > return 0; > > - return xen_cpuid_base(); > + base = xen_cpuid_base(); > + if (!base) > + return 0; > + > + cpuid(base + 1, &eax, &ebx, &ecx, &edx); > + > + xen_major = eax >> 16; > + xen_minor = eax & 0xffff; > + > + printk(KERN_INFO "Xen version %d.%d.\n", xen_major, xen_minor); > + > + return 1; You appear to have changed to return value here? Did you mean to return base here? David _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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