Re: [PATCH 21/35] KVM: s390/mm: handle guest unpin events

[Thomas Huth <thuth@redhat.com>]

On 07/02/2020 12.39, Christian Borntraeger wrote:
> From: Claudio Imbrenda <imbrenda@linux.ibm.com>
> 
> The current code tries to first pin shared pages, if that fails (e.g.
> because the page is not shared) it will export them. For shared pages
> this means that we get a new intercept telling us that the guest is
> unsharing that page. We will make the page secure at that point in time
> and revoke the host access. This is synchronized with other host events,
> e.g. the code will wait until host I/O has finished.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> [borntraeger@de.ibm.com: patch merging, splitting, fixing]
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  arch/s390/kvm/intercept.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
> index 2a966dc52611..e155389a4a66 100644
> --- a/arch/s390/kvm/intercept.c
> +++ b/arch/s390/kvm/intercept.c
> @@ -16,6 +16,7 @@
>  #include <asm/asm-offsets.h>
>  #include <asm/irq.h>
>  #include <asm/sysinfo.h>
> +#include <asm/uv.h>
>  
>  #include "kvm-s390.h"
>  #include "gaccess.h"
> @@ -484,12 +485,35 @@ static int handle_pv_sclp(struct kvm_vcpu *vcpu)
>  	return 0;
>  }
>  
> +static int handle_pv_uvc(struct kvm_vcpu *vcpu)
> +{
> +	struct uv_cb_share *guest_uvcb = (void *)vcpu->arch.sie_block->sidad;
> +	struct uv_cb_cts uvcb = {
> +		.header.cmd	= UVC_CMD_UNPIN_PAGE_SHARED,
> +		.header.len	= sizeof(uvcb),
> +		.guest_handle	= kvm_s390_pv_handle(vcpu->kvm),
> +		.gaddr		= guest_uvcb->paddr,
> +	};
> +	int rc;
> +
> +	if (guest_uvcb->header.cmd != UVC_CMD_REMOVE_SHARED_ACCESS) {
> +		WARN_ONCE(1, "Unexpected UVC 0x%x!\n", guest_uvcb->header.cmd);

Is there a way to signal the failed command to the guest, too?

 Thomas


> +		return 0;
> +	}
> +	rc = uv_make_secure(vcpu->arch.gmap, uvcb.gaddr, &uvcb);
> +	if (rc == -EINVAL && uvcb.header.rc == 0x104)
> +		return 0;
> +	return rc;
> +}
> +
>  static int handle_pv_notification(struct kvm_vcpu *vcpu)
>  {
>  	if (vcpu->arch.sie_block->ipa == 0xb210)
>  		return handle_pv_spx(vcpu);
>  	if (vcpu->arch.sie_block->ipa == 0xb220)
>  		return handle_pv_sclp(vcpu);
> +	if (vcpu->arch.sie_block->ipa == 0xb9a4)
> +		return handle_pv_uvc(vcpu);
>  
>  	return handle_instruction(vcpu);
>  }
>