Re: [PATCH 0/2] MMIO emulation fixes

From: Olaf Hering <olaf@aepfle.de>
To: Jan Beulich <JBeulich@suse.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Paul Durrant <paul.durrant@citrix.com>,
	george.dunlap@citrix.com,
	xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH 0/2] MMIO emulation fixes
Date: Thu, 30 Aug 2018 12:42:43 +0200	[thread overview]
Message-ID: <20180830104243.GB20226@aepfle.de> (raw)
In-Reply-To: <5B87A97D02000078001E3674@prv1-mh.provo.novell.com>

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On Thu, Aug 30, Jan Beulich wrote:

> approach): One is Paul's idea of making null_handler actually retrieve
> RAM contents when (part of) the access touches RAM. Another might

This works for me:

static int null_read(const struct hvm_io_handler *io_handler,
                     uint64_t addr,
                     uint32_t size,
                     uint64_t *data)
{
    struct vcpu *curr = current;
    struct domain *currd = curr->domain;
    p2m_type_t p2mt = p2m_invalid;
    unsigned long gmfn = paddr_to_pfn(addr);
    struct page_info *page;
    char *p;

    get_gfn_query_unlocked(currd, gmfn, &p2mt);
    if ( p2mt != p2m_ram_rw )
    {   
        *data = ~0ul;
    }
    else
    {   
        page = get_page_from_gfn(currd, gmfn, NULL, P2M_UNSHARE);
        if ( ! page )
        {
            memset(data, 0xee, size);
        }
        else
        {
            p = (char *)__map_domain_page(page) + (addr & ~PAGE_MASK);
            memcpy(data, p, size);
            unmap_domain_page(p);
            put_page(page);
        }
    }
    return X86EMUL_OKAY;
}

Olaf

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