Re: [PATCH 2/4] powerpc kvm: added multiple TCEs requests support
From: Alexey Kardashevskiy
Date: Mon Feb 18 2013 - 03:14:47 EST
On 15/02/13 14:24, Paul Mackerras wrote:
On Mon, Feb 11, 2013 at 11:12:41PM +1100, aik@xxxxxxxxx wrote:
+static long emulated_h_put_tce(struct kvmppc_spapr_tce_table *stt,
+ unsigned long ioba, unsigned long tce)
+{
+ unsigned long idx = ioba >> SPAPR_TCE_SHIFT;
+ struct page *page;
+ u64 *tbl;
+
+ /* udbg_printf("H_PUT_TCE: liobn 0x%lx => stt=%p window_size=0x%x\n", */
+ /* liobn, stt, stt->window_size); */
+ if (ioba >= stt->window_size) {
+ pr_err("%s failed on ioba=%lx\n", __func__, ioba);
Doesn't this give the guest a way to spam the host logs? And in fact
printk in real mode is potentially problematic. I would just leave
out this statement.
+ return H_PARAMETER;
+ }
+
+ page = stt->pages[idx / TCES_PER_PAGE];
+ tbl = (u64 *)page_address(page);
I would like to see an explanation of why we are confident that
page_address() will work correctly in real mode, across all the
combinations of config options that we can have for a ppc64 book3s
kernel.
It was there before this patch, I just moved it so I would think it has
been explained before :)
There is no combination on PPC to get WANT_PAGE_VIRTUAL enabled.
CONFIG_HIGHMEM is supported for PPC32 only so HASHED_PAGE_VIRTUAL is not
enabled on PPC64 either.
So this definition is supposed to work on PPC64:
#define page_address(page) lowmem_page_address(page)
where lowmem_page_address() is arithmetic operation on a page struct address:
static __always_inline void *lowmem_page_address(const struct page *page)
{
return __va(PFN_PHYS(page_to_pfn(page)));
}
PPC32 will use page_address() from mm/highmem.c, I need some lesson about
memory layout in 32bit but for now I cannot see how it can possibly fail here.
+
+ /* FIXME: Need to validate the TCE itself */
+ /* udbg_printf("tce @ %p\n", &tbl[idx % TCES_PER_PAGE]); */
+ tbl[idx % TCES_PER_PAGE] = tce;
+
+ return H_SUCCESS;
+}
+
+/*
+ * Real mode handlers
*/
long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
unsigned long ioba, unsigned long tce)
{
- struct kvm *kvm = vcpu->kvm;
struct kvmppc_spapr_tce_table *stt;
- /* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
- /* liobn, ioba, tce); */
+ stt = find_tce_table(vcpu, liobn);
+ /* Didn't find the liobn, put it to userspace */
+ if (!stt)
+ return H_TOO_HARD;
+
+ /* Emulated IO */
+ return emulated_h_put_tce(stt, ioba, tce);
+}
+
+long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
+ unsigned long liobn, unsigned long ioba,
+ unsigned long tce_list, unsigned long npages)
+{
+ struct kvmppc_spapr_tce_table *stt;
+ long i, ret = 0;
+ unsigned long *tces;
+
+ stt = find_tce_table(vcpu, liobn);
+ /* Didn't find the liobn, put it to userspace */
+ if (!stt)
+ return H_TOO_HARD;
- list_for_each_entry(stt, &kvm->arch.spapr_tce_tables, list) {
- if (stt->liobn == liobn) {
- unsigned long idx = ioba >> SPAPR_TCE_SHIFT;
- struct page *page;
- u64 *tbl;
+ tces = (void *) get_real_address(vcpu, tce_list, false, NULL, NULL);
+ if (!tces)
+ return H_TOO_HARD;
- /* udbg_printf("H_PUT_TCE: liobn 0x%lx => stt=%p window_size=0x%x\n", */
- /* liobn, stt, stt->window_size); */
- if (ioba >= stt->window_size)
- return H_PARAMETER;
+ /* Emulated IO */
+ for (i = 0; (i < npages) && !ret; ++i, ioba += IOMMU_PAGE_SIZE)
+ ret = emulated_h_put_tce(stt, ioba, tces[i]);
So, tces is a pointer to somewhere inside a real page. Did we check
somewhere that tces[npages-1] is in the same page as tces[0]? If so,
I missed it. If we didn't, then we probably should check and do
something about it.
- page = stt->pages[idx / TCES_PER_PAGE];
- tbl = (u64 *)page_address(page);
+ return ret;
+}
- /* FIXME: Need to validate the TCE itself */
- /* udbg_printf("tce @ %p\n", &tbl[idx % TCES_PER_PAGE]); */
- tbl[idx % TCES_PER_PAGE] = tce;
- return H_SUCCESS;
- }
- }
+long kvmppc_h_stuff_tce(struct kvm_vcpu *vcpu,
+ unsigned long liobn, unsigned long ioba,
+ unsigned long tce_value, unsigned long npages)
+{
+ struct kvmppc_spapr_tce_table *stt;
+ long i, ret = 0;
+
+ stt = find_tce_table(vcpu, liobn);
+ /* Didn't find the liobn, put it to userspace */
+ if (!stt)
+ return H_TOO_HARD;
- /* Didn't find the liobn, punt it to userspace */
- return H_TOO_HARD;
+ /* Emulated IO */
+ for (i = 0; (i < npages) && !ret; ++i, ioba += IOMMU_PAGE_SIZE)
+ ret = emulated_h_put_tce(stt, ioba, tce_value);
+
+ return ret;
+}
+
+/*
+ * Virtual mode handlers
+ */
+extern long kvmppc_virtmode_h_put_tce(struct kvm_vcpu *vcpu,
+ unsigned long liobn, unsigned long ioba,
+ unsigned long tce)
+{
+ /* At the moment emulated IO is handled the same way */
+ return kvmppc_h_put_tce(vcpu, liobn, ioba, tce);
+}
+
+extern long kvmppc_virtmode_h_put_tce_indirect(struct kvm_vcpu *vcpu,
+ unsigned long liobn, unsigned long ioba,
+ unsigned long tce_list, unsigned long npages)
+{
+ struct kvmppc_spapr_tce_table *stt;
+ unsigned long *tces;
+ long ret = 0, i;
+
+ stt = find_tce_table(vcpu, liobn);
+ /* Didn't find the liobn, put it to userspace */
+ if (!stt)
+ return H_TOO_HARD;
+
+ tces = (void *) get_virt_address(vcpu, tce_list, false, NULL, NULL);
+ if (!tces)
+ return H_TOO_HARD;
+
+ /* Emulated IO */
+ for (i = 0; (i < npages) && !ret; ++i, ioba += IOMMU_PAGE_SIZE)
+ ret = emulated_h_put_tce(stt, ioba, tces[i]);
Same comment here about tces[i] overflowing a page boundary.
+
+ return ret;
+}
+
+extern long kvmppc_virtmode_h_stuff_tce(struct kvm_vcpu *vcpu,
+ unsigned long liobn, unsigned long ioba,
+ unsigned long tce_value, unsigned long npages)
+{
+ /* At the moment emulated IO is handled the same way */
+ return kvmppc_h_stuff_tce(vcpu, liobn, ioba, tce_value, npages);
}
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 71d0c90..13c8436 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -515,6 +515,29 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
kvmppc_get_gpr(vcpu, 5),
kvmppc_get_gpr(vcpu, 6));
break;
+ case H_PUT_TCE:
+ ret = kvmppc_virtmode_h_put_tce(vcpu, kvmppc_get_gpr(vcpu, 4),
+ kvmppc_get_gpr(vcpu, 5),
+ kvmppc_get_gpr(vcpu, 6));
+ if (ret == H_TOO_HARD)
+ return RESUME_HOST;
+ break;
+ case H_PUT_TCE_INDIRECT:
+ ret = kvmppc_virtmode_h_put_tce_indirect(vcpu, kvmppc_get_gpr(vcpu, 4),
+ kvmppc_get_gpr(vcpu, 5),
+ kvmppc_get_gpr(vcpu, 6),
+ kvmppc_get_gpr(vcpu, 7));
+ if (ret == H_TOO_HARD)
+ return RESUME_HOST;
+ break;
+ case H_STUFF_TCE:
+ ret = kvmppc_virtmode_h_stuff_tce(vcpu, kvmppc_get_gpr(vcpu, 4),
+ kvmppc_get_gpr(vcpu, 5),
+ kvmppc_get_gpr(vcpu, 6),
+ kvmppc_get_gpr(vcpu, 7));
+ if (ret == H_TOO_HARD)
+ return RESUME_HOST;
+ break;
default:
return RESUME_HOST;
}
[snip]
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 70739a0..95614c7 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -383,6 +383,9 @@ int kvm_dev_ioctl_check_extension(long ext)
r = 1;
break;
#endif
+ case KVM_CAP_PPC_MULTITCE:
+ r = 1;
+ break;
default:
r = 0;
break;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index e6e5d4b..26e2b271 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -635,6 +635,7 @@ struct kvm_ppc_smmu_info {
#define KVM_CAP_IRQFD_RESAMPLE 82
#define KVM_CAP_PPC_BOOKE_WATCHDOG 83
#define KVM_CAP_PPC_HTAB_FD 84
+#define KVM_CAP_PPC_MULTITCE 87
The capability should be described in
Documentation/virtual/kvm/api.txt.
Is it enough description?
===
4.79 KVM_CAP_PPC_MULTITCE
Architectures: ppc
Parameters: none
Returns: 0 on success; -1 on error
This capability enables the guest to put/remove multiple TCE entries
per hypercall which significanly accelerates DMA operations for PPC KVM
guests.
When this capability is enabled, H_PUT_TCE_INDIRECT and H_STUFF_TCE are
expected to occur rather than H_PUT_TCE which supports only one TCE entry
per call.
===
--
Alexey
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