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Mon, 15 Jul 2024 08:00:43 -0700 (PDT) Message-ID: Date: Mon, 15 Jul 2024 17:00:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 8/8] xen/riscv: introduce early_fdt_map() From: Jan Beulich To: Oleksii Cc: Alistair Francis , Bob Eshleman , Connor Davis , Andrew Cooper , Julien Grall , Stefano Stabellini , xen-devel@lists.xenproject.org References: <4e4f94817fb3bba5f52336ea0b4491f7bc867d49.1720799926.git.oleksii.kurochko@gmail.com> <945afaf1-8223-4e3e-bf6d-98a6fad66f78@suse.com> Content-Language: en-US Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: <945afaf1-8223-4e3e-bf6d-98a6fad66f78@suse.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 15.07.2024 16:58, Jan Beulich wrote: > On 15.07.2024 15:58, Oleksii wrote: >> On Mon, 2024-07-15 at 10:52 +0200, Jan Beulich wrote: >>> On 12.07.2024 18:22, Oleksii Kurochko wrote: >>>> +    rc = map_pages_to_xen(BOOT_FDT_VIRT_START, >>>> maddr_to_mfn(base_paddr), >>>> +                          SZ_2M >> PAGE_SHIFT, >>>> +                          PAGE_HYPERVISOR_RO | _PAGE_BLOCK); >>>> +    if ( rc ) >>>> +        panic("Unable to map the device-tree.\n"); >>>> + >>>> +    offset = fdt_paddr % XEN_PT_LEVEL_SIZE(1); >>>> +    fdt_virt = (void *)BOOT_FDT_VIRT_START + offset; >>>> + >>>> +    if ( fdt_magic(fdt_virt) != FDT_MAGIC ) >>>> +        return NULL; >>>> + >>>> +    size = fdt_totalsize(fdt_virt); >>>> +    if ( size > BOOT_FDT_VIRT_SIZE ) >>>> +        return NULL; >>>> + >>>> +    if ( (offset + size) > SZ_2M ) >>>> +    { >>>> +        rc = map_pages_to_xen(BOOT_FDT_VIRT_START + SZ_2M, >>>> +                              maddr_to_mfn(base_paddr + SZ_2M), >>>> +                              SZ_2M >> PAGE_SHIFT, >>>> +                              PAGE_HYPERVISOR_RO | _PAGE_BLOCK); >>>> +        if ( rc ) >>>> +            panic("Unable to map the device-tree\n"); >>>> +    } >>> >>> Why this two part mapping? And why are you mapping perhaps much more >>> than "size"? >> I wasn't able to find if RISC-V has a requirement for alignment of FDT >> address so I decided to follow Arm where FDT is required to be placed >> on a 8-byte boundary, so FDT can cross a 2MB boundary, so the second >> 2MB page should be mapped if the FDT is crossing the 2MB boundary. > > This explains why you may need to map more than 2Mb (which wasn't the > question), but it doesn't explain why you need to do it in two steps. Oh, wait - you know the full size only after having mapped the initial part. I'm sorry, I didn't spot that early enough. Jan