From: Christian Ehrhardt <[EMAIL PROTECTED]> This patch adds the guest handling for the magic page mechanism. A Hypervisor can modify the device tree passed to the guest. Using that already existing interface a guest can simply detect available hypervisor features and agree on the supported ones using hypercalls. In this example it is checked for the feature switch "feature,pv-magicpage" in the hypervisor node and additional data which represents the size the hypervisor requests in "data,pv-magicpage-size". When the guest reads that data and wants to support it the memory is allocated and passed to the hypervisor using the KVM_HCALL_RESERVE_MAGICPAGE hypercall.
Signed-off-by: Christian Ehrhardt <[EMAIL PROTECTED]> --- [diffstat] arch/powerpc/kernel/kvm.c | 51 +++++++++++++++++++++++++++++++++++++++++ include/asm-powerpc/fixmap.h | 10 +++++++- include/asm-powerpc/kvm_para.h | 26 ++++++++++++++++++++ mm/page_alloc.c | 1 4 files changed, 87 insertions(+), 1 deletion(-) [diff] diff --git a/arch/powerpc/kernel/kvm.c b/arch/powerpc/kernel/kvm.c --- a/arch/powerpc/kernel/kvm.c +++ b/arch/powerpc/kernel/kvm.c @@ -22,9 +22,60 @@ #include <linux/percpu.h> #include <linux/mm.h> #include <linux/kvm_para.h> +#include <linux/bootmem.h> +#include <asm/fixmap.h> + +/* + * this is guest memory granted to the hypervisor; + * the hypervisor can place data in this area and rewrite + * privileged instructions to read from this area without + * trapping. + * Only the Hypervisor needs to be aware of the structure layout + * which makes the guest more felxible - the guest only guarantees + * the size which is requested by the hypervisor and read from a + * device tree entry. + */ +static void *kvm_magicpage; + +static void __init kvmppc_register_magic_page(void) +{ + unsigned long gvaddr; + unsigned long gpaddr; + int size; + long err; + + size = kvmppc_pv_read_data(KVM_PVDATA_MAGICPAGE_SIZE); + if (size < 0) { + printk(KERN_ERR "%s: couldn't read size for kvmppc style " + "paravirtualization support (got %d)\n", + __func__, size); + return; + } + + /* FIXME Guest SMP needs that percpu which */ + kvm_magicpage = alloc_bootmem(size); + if (!kvm_magicpage) { + printk(KERN_ERR "%s - failed to allocate %d bytes\n", + __func__, size); + return; + } + gpaddr = (unsigned long)__pa(kvm_magicpage); + gvaddr = fix_to_virt(FIX_KVM_PV); + + err = kvm_hypercall2(KVM_HCALL_RESERVE_MAGICPAGE, gvaddr, gpaddr); + if (err) + printk(KERN_ERR "%s: couldn't register pv mem\n", __func__); + else + printk(KERN_NOTICE "%s: registered %d bytes for pv mem support" + " (gvaddr 0x%08lx gpaddr 0x%08lx)\n", + __func__, size, gvaddr, gpaddr); +} void __init kvm_guest_init(void) { if (!kvm_para_available()) return; + + if (kvm_para_has_feature(KVM_FEATURE_PPCPV_MAGICPAGE)) + kvmppc_register_magic_page(); } diff --git a/include/asm-powerpc/fixmap.h b/include/asm-powerpc/fixmap.h --- a/include/asm-powerpc/fixmap.h +++ b/include/asm-powerpc/fixmap.h @@ -36,7 +36,7 @@ * * these 'compile-time allocated' memory buffers are * fixed-size 4k pages. (or larger if used with an increment - * highger than 1) use fixmap_set(idx,phys) to associate + * higher than 1) use fixmap_set(idx,phys) to associate * physical memory with fixmap indices. * * TLB entries of such buffers will not be flushed across @@ -44,6 +44,14 @@ */ enum fixed_addresses { FIX_HOLE, +#ifdef CONFIG_KVM_GUEST + /* + * reserved virtual address space for paravirtualization - needs to be + * <=32k away from base address 0 to be able to reach it with + * immediate addressing using base 0 instead of needing a register. + */ + FIX_KVM_PV, +#endif #ifdef CONFIG_HIGHMEM FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */ FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1, diff --git a/include/asm-powerpc/kvm_para.h b/include/asm-powerpc/kvm_para.h --- a/include/asm-powerpc/kvm_para.h +++ b/include/asm-powerpc/kvm_para.h @@ -28,10 +28,18 @@ #define KVM_HYPERCALL_BIN 0x03ffffff +#define KVM_HCALL_RESERVE_MAGICPAGE 0 + +#define KVM_PVDATA_MAGICPAGE_SIZE "data,pv-magicpage-size" + +/* List of PV features supported, returned as a bitfield */ +#define KVM_FEATURE_PPCPV_MAGICPAGE 0 + static struct kvmppc_para_features { char *dtcell; int feature; } para_features[] = { + { "feature,pv-magicpage", KVM_FEATURE_PPCPV_MAGICPAGE } }; static inline int kvm_para_available(void) @@ -67,6 +75,24 @@ of_node_put(dn); return features; +} + +/* reads the specified data field out of the hypervisor node */ +static inline int kvmppc_pv_read_data(char *dtcell) +{ + struct device_node *dn; + const int *dtval; + + dn = of_find_node_by_path("/hypervisor"); + if (!dn) + return -EINVAL; + + dtval = of_get_property(dn, dtcell, NULL); + of_node_put(dn); + if (dtval) + return *dtval; + else + return -EINVAL; } void kvm_guest_init(void); diff --git a/mm/page_alloc.c b/mm/page_alloc.c --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -550,6 +550,7 @@ prefetchw(p + 1); __ClearPageReserved(p); set_page_count(p, 0); + } set_page_refcounted(page); _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev