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    Subject[RFCv2 03/13] x86/kvm: Make DMA pages shared
    Date
    Make force_dma_unencrypted() return true for KVM to get DMA pages mapped
    as shared.

    __set_memory_enc_dec() now informs the host via hypercall if the state
    of the page has changed from shared to private or back.

    Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    ---
    arch/x86/Kconfig | 1 +
    arch/x86/mm/mem_encrypt_common.c | 5 +++--
    arch/x86/mm/pat/set_memory.c | 10 ++++++++++
    include/uapi/linux/kvm_para.h | 1 +
    4 files changed, 15 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    index 2b4ce1722dbd..d197b3beb904 100644
    --- a/arch/x86/Kconfig
    +++ b/arch/x86/Kconfig
    @@ -811,6 +811,7 @@ config KVM_GUEST
    select PARAVIRT_CLOCK
    select ARCH_CPUIDLE_HALTPOLL
    select X86_HV_CALLBACK_VECTOR
    + select X86_MEM_ENCRYPT_COMMON
    default y
    help
    This option enables various optimizations for running under the KVM
    diff --git a/arch/x86/mm/mem_encrypt_common.c b/arch/x86/mm/mem_encrypt_common.c
    index dd791352f73f..6bf0718bb72a 100644
    --- a/arch/x86/mm/mem_encrypt_common.c
    +++ b/arch/x86/mm/mem_encrypt_common.c
    @@ -10,14 +10,15 @@
    #include <linux/mm.h>
    #include <linux/mem_encrypt.h>
    #include <linux/dma-direct.h>
    +#include <asm/kvm_para.h>

    /* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
    bool force_dma_unencrypted(struct device *dev)
    {
    /*
    - * For SEV, all DMA must be to unencrypted/shared addresses.
    + * For SEV and KVM, all DMA must be to unencrypted/shared addresses.
    */
    - if (sev_active())
    + if (sev_active() || kvm_mem_protected())
    return true;

    /*
    diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
    index 16f878c26667..4b312d80033d 100644
    --- a/arch/x86/mm/pat/set_memory.c
    +++ b/arch/x86/mm/pat/set_memory.c
    @@ -16,6 +16,7 @@
    #include <linux/pci.h>
    #include <linux/vmalloc.h>
    #include <linux/libnvdimm.h>
    +#include <linux/kvm_para.h>

    #include <asm/e820/api.h>
    #include <asm/processor.h>
    @@ -1977,6 +1978,15 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
    struct cpa_data cpa;
    int ret;

    + if (kvm_mem_protected()) {
    + /* TODO: Unsharing memory back */
    + if (WARN_ON_ONCE(enc))
    + return -ENOSYS;
    +
    + return kvm_hypercall2(KVM_HC_MEM_SHARE,
    + __pa(addr) >> PAGE_SHIFT, numpages);
    + }
    +
    /* Nothing to do if memory encryption is not active */
    if (!mem_encrypt_active())
    return 0;
    diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
    index 1a216f32e572..09d36683ee0a 100644
    --- a/include/uapi/linux/kvm_para.h
    +++ b/include/uapi/linux/kvm_para.h
    @@ -30,6 +30,7 @@
    #define KVM_HC_SEND_IPI 10
    #define KVM_HC_SCHED_YIELD 11
    #define KVM_HC_ENABLE_MEM_PROTECTED 12
    +#define KVM_HC_MEM_SHARE 13

    /*
    * hypercalls use architecture specific
    --
    2.26.3
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