Re: [PATCH 2/4] powerpc kvm: added multiple TCEs requests support

Paul Mackerras
2013-02-15T03:24:59Z

On Mon, Feb 11, 2013 at 11:12:41PM +1100, aik@ozlabs.ru 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.

> +
> + /* 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.

Paul.